Which is wider — mainland Australia or the Moon?

Mainland Australia stretches roughly 4,000 kilometers from its eastern to western coasts, while the Moon measures only about 3,475 kilometers across at its widest point. That means a single country here on Earth is physically wider than an entire moon, a comparison that feels counterintuitive since we tend to imagine any celestial body as larger than any feature on our own planet.

Saying the two are about equal understates the gap, Australia's width exceeds the Moon's diameter by several hundred kilometers, a meaningful difference rather than a near-tie, even though both numbers are in the same general range of thousands of kilometers.

The Moon's modest size relative to Earth, only about a quarter of Earth's diameter, is unusually large for a moon in proportion to its host planet, which is part of why some astronomers describe the Earth-Moon system almost as a double-planet arrangement rather than a typical planet-and-satellite pair.